الله الله بسم بسمالرحيم الرحيم الرحمن الرحمن

LIVER, PANCREAS & SPLEENLIVER, PANCREAS & SPLEEN

Objectives: Objectives: By the end of this lecture, the By the end of this lecture, the student should be able to describe:student should be able to describe:

1.1.The histological structure of The histological structure of liverliver with with special emphasis on the classic hepatic special emphasis on the classic hepatic lobule.lobule.

2.2.The histological structure of exocrine The histological structure of exocrine portion of portion of pancreaspancreas..

3.3.The histological features of The histological features of spleenspleen..

LIVERLIVER

1-1- Stroma:Stroma:

a-a- Capsule: Capsule: Glisson’s Capsule.Glisson’s Capsule.

b-b- Septa (absent in Septa (absent in human) & Portal areas human) & Portal areas (Portal tracts).(Portal tracts).

c-c- Network of Network of reticular fibers.reticular fibers.

2-2- Parenchyma; Classic Parenchyma; Classic liver (hepatic) lobules.liver (hepatic) lobules.

Pig’s liverPig’s liver

CLASSIC LIVER LOBULECLASSIC LIVER LOBULE(classical hepatic lobule)(classical hepatic lobule)

It is formed of a It is formed of a polygonal masspolygonal mass of of liver tissue, with portal liver tissue, with portal areas at the areas at the peripheryperiphery & central (centrolobular) & central (centrolobular) vein in the vein in the centercenter..

Human liverHuman liver

Contents of the Classic Liver LobuleContents of the Classic Liver Lobule

1-1- Anastomosing Anastomosing plates of plates of hepatocyteshepatocytes..

2-2- Liver sinusoids (Liver sinusoids (hepatic hepatic blood sinusoidsblood sinusoids): In ): In between the plates.between the plates.

3-3- Spaces of Disse Spaces of Disse (perisinusoidal spaces of (perisinusoidal spaces of Disse).Disse).

4-4- Central veinCentral vein..

5-5- Bile canaliculiBile canaliculi..

Borders of the Classical Liver LobuleBorders of the Classical Liver Lobule

1-1- Septa: Septa: C.T. septa (e.g. in C.T. septa (e.g. in pigs).pigs).

2-2- Portal areas Portal areas (Portal tracts):(Portal tracts):

Are located in the corners Are located in the corners of the classic hepatic of the classic hepatic lobule (usually 3 in No.).lobule (usually 3 in No.).

Contents of portal area:Contents of portal area:

a-a- C.T.C.T.

b-b- Bile ducts (interlobular bile Bile ducts (interlobular bile ducts).ducts).

c-c- Venule (Branch of portal Venule (Branch of portal vein).vein).

d-d- Arteriole ( Branch of Arteriole ( Branch of hepatic artery). hepatic artery).

Hepatocytes (LM)Hepatocytes (LM)

Are grouped in interconnected Are grouped in interconnected plates.plates.

Liver sinusoids are located in Liver sinusoids are located in the spaces between these the spaces between these plates.plates.

Are polyhedral in shape.Are polyhedral in shape. Nucleus: 1 or 2, vesicular with Nucleus: 1 or 2, vesicular with

prominent nucleoli.prominent nucleoli. Cytoplasm: acidophilic.Cytoplasm: acidophilic.

Hepatocytes (EM)Hepatocytes (EM)Organelles:Organelles:

1- Mitochondria: ++++1- Mitochondria: ++++

2- ER (sER & rER): abundant.2- ER (sER & rER): abundant.

3- Golgi complex.3- Golgi complex.

4- Lysosomes.4- Lysosomes.

5- Peroxisomes.5- Peroxisomes.

Inclusions (Deposits):Inclusions (Deposits):

1- Glycogen 2- Lipid (few droplets).1- Glycogen 2- Lipid (few droplets).

3- Lipofuscin (old age)3- Lipofuscin (old age)

Liver SinusoidsLiver Sinusoids

(1) Endothelial Cells:(1) Endothelial Cells:– Fenestrated & Fenestrated &

discontinuous → free discontinuous → free passage of plasma.passage of plasma.

– Basal lamina is absent.Basal lamina is absent.

(2) Kupffer Cells:(2) Kupffer Cells:– Are macrophages.Are macrophages.– Are found on the Are found on the

luminal surface of the luminal surface of the endothelial cells. endothelial cells.

– Function: phagocytosis.Function: phagocytosis.

Space of Disse (Perisinusoidal Space)Space of Disse (Perisinusoidal Space)

Contents:Contents:

1- Fat-storing cells (Ito cells):1- Fat-storing cells (Ito cells):– contain vitamin A-rich lipid.contain vitamin A-rich lipid.– form reticulin.form reticulin.

2- Reticular fibers:2- Reticular fibers:(type III collagen).(type III collagen).

3- Plasma 3- Plasma of blood.of blood.

4- Microvilli 4- Microvilli of hepatocytes.of hepatocytes.

PancreasPancreas

EXOCRINE PORTION OF PANCREASEXOCRINE PORTION OF PANCREAS

(A)(A) Stroma: Stroma: capsule, septa & reticular fibers.capsule, septa & reticular fibers.

(B)(B) Parenchyma:Parenchyma:

- Pancreatic acini:- Pancreatic acini:– Acini with Acini with centroacinar cellscentroacinar cells..– No myoepithelial cellsNo myoepithelial cells..

- Duct system:- Duct system:– Centroacinar cells, intercalated ducts (low cuboidal), Centroacinar cells, intercalated ducts (low cuboidal),

intralobular ducts (intralobular ducts (NOT prominentNOT prominent), interlobular ducts.), interlobular ducts.

– N.B. N.B. No striated ductsNo striated ducts..

Pancreatic Acinar CellsPancreatic Acinar Cells

They are pyramidal cells They are pyramidal cells characterized by:characterized by:The apical cytoplasm The apical cytoplasm ((acidophilicacidophilic) is rich in ) is rich in zymogenic granules.zymogenic granules.The basal cytoplasm is The basal cytoplasm is rich in RER, so it is rich in RER, so it is basophilicbasophilic..The nucleus is The nucleus is basalbasal in in positionposition..

SPLEENSPLEEN

Stroma of SpleenStroma of Spleen

1-1- Capsule:Capsule:– is covered by visceral is covered by visceral

layer of peritoneum; layer of peritoneum; mesothelium.mesothelium.

– occasionally contains occasionally contains smooth muscle cells smooth muscle cells (SMCs).(SMCs).

2-2- Trabeculae: Trabeculae: irregular.irregular.

3-3- Reticular C.T.Reticular C.T.

Parenchyma of SpleenParenchyma of Spleen

(A) White pulp.(A) White pulp.

(B) Red pulp.(B) Red pulp.

N.B.N.B. No cortex, No cortex,

No medulla, No medulla,

No afferent lymphatic vessel.No afferent lymphatic vessel.

Parenchyma of SpleenParenchyma of Spleen

White Pulp:White Pulp:

1-1- Periarterial lymphatic Periarterial lymphatic sheaths (PALS)sheaths (PALS):: housing T lymphocytes.housing T lymphocytes.

2-2- Lymphoid nodulesLymphoid nodules (with (with germinal centers): germinal centers): housing B lymphocytes.housing B lymphocytes.

N.B.N.B. Both 1&2 have the Both 1&2 have the acentrically located acentrically located central artery (central central artery (central arteriole). arteriole).

Parenchyma of SpleenParenchyma of Spleen

(B)(B) Red pulp:Red pulp: 1-1- Pulp (splenic) cords:Pulp (splenic) cords:

Extravasated Extravasated blood cellsblood cells, , plasma cells, plasma cells, macrophagesmacrophages & & reticular cells and fibers.reticular cells and fibers.2-2- Blood sinusoids:Blood sinusoids:

Are lined with elongated Are lined with elongated fusiform fusiform endothelial cellsendothelial cells with with large large intercellular spacesintercellular spaces & & supported by supported by discontinuous, discontinuous, circular basement membranecircular basement membrane..

Splenic MicrocirculationSplenic Microcirculation

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